The present invention relates to devices for sensing the speed of an object, typically a rotating object, and in particular to such a device operable for generating a light pulse signal as a function of speed that is transmittable by means of a fiber optic conductor to a remote display and/or control device.
Electronic devices are being increasingly utilized to sense and manage the operation of machinery. In one such application, such electronic devices are utilized in electronic engine controls for gas turbine engines. In another such application, such control devices are utilized to monitor the rotational behavior of a vehicle's wheels and to control the application of braking pressure to avert skids.
In yet another application, such control devices are utilized to respond to manual commands operator inputs, to alternate the outputs of the control.
In the case of speed sensors used in antiskid systems such as Class B and C antilock brake systems for passenger cars, accurate speed sensing is needed at low wheel speeds. Antiskid traction systems must detect slight wheel movement in order to detect impending loss of traction at low speeds.
In the case of an electronic engine control, it is increasingly desirable to limit if not eliminate, the use of electrical conductors between sensors and controllers and the electronic control units to reduce the effects of EMI and EMP, lightning and other induced electrical noise. In the case of automotive applications, fiber optic connections substantially reduce in effect of the various sources of electronic noise such as alternators, ignition systems, and the like.
One particular type of transducer utilized in such systems is a speed transducer, that is, a device which generates a signal proportional to the speed of a machine such as a turbine engine or the wheel of a motor vehicle. Heretofore, transducers for generating such a speed signal have used electrical conductors to communicate with a remote electronic control or display or, in the alternative, have incorporated relatively expensive circuits for generating a light pulse signal suitable for transmission to the electronic control unit. As a result there exists a need for an improved speed transducer which produces a speed signal suitable for transmission by means of fiber optics without an external electrical power source in addition to being rugged, and relatively inexpensive.
It is therefore an object of the invention to provide an improved speed transducer. Another object of the invention is to provide such a transducer which produces a light pulse signal proportional to speed of an object. Another object of the invention is to provide a sensor system which can not only monitor the rotating speed of a shaft but can also be used to provide a signal proportional to a discrete switch position.